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Message: <blockquote data-quote="typo" data-source="post: 3280693" data-attributes="member: 83808">Chosun,I'm not that familiar with camera lens MTFs but some reviewers at least draw a distinction between contrast at 60 cycles per degree and 20 cycles per degree to approximate to categorise high resolution and 'sharpness'. A high 60cpd value will be high resolution. A lens with a low 60cpd value but high 20cpd value will be sharp. This is based on certain presumptions about the size and viewing distance of the resulting print. It is often complicated by these relative values changing with f-number.There is the potential for binocular designers to manipulate performance in the same way. It's unclear to me if they do deliberately, but it is evident that differences do exist all the same. Most binocular users will have an optimum acuity between 30 and 60 cycles per degree when the light is sufficient to contract their pupils to about 2.5mm. A perfect optic would deliver around 75cpd at the corresponding objective diameter for an 8x. In fact many better binoculars are between 60 and 75cpd. However, visually we perceive optimal 'sharpness' between 6 and 10 cpd. A binocular with poor resolution but high contrast at 6 to 10cpd would appear 'sharper' even though it was lacking in detail. At the time I reckoned the HT 8x54 would have an effective resolution value for a 20mm stopped down objective of about 9 arcseconds which would be about 50cpd or more typical of sub-£200 models. I think the Swaro CL is worse still.The DIN ISO shandard prevents the big names from making a binocular that is really really tuned for 'sharpness' alone, but it's clear there are contrast differences in the 6 to 60cpd regions which can alter perceptions of effective resolution and 'sharpness'.David</blockquote>

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